Priming composition

ABSTRACT

Granulated initiator explosive composition having a weight ratio of 5:95 to 95:5 of lead azide to lead trinitroresorcinate and 0.1 to 0.5 weight percent binder calculated on total weight of the composition.

Unite States aient Inventors Josef Prior [56] References Cited UNITEDSTATES PATENTS 2,295,104 9/1942 Garfield 149/26 X 2,421,778 6/1947Fleischer et al... 149/26 2,464,777 3/1949 Rubenstein et a1. 149/26 X3,291,663 12/1966 Taylor et a1 149/26 X FOREIGN PATENTS 156,429 1/1921Great Britain 149/26 Primary Examiner Leland A. SebastianAttorney-Burgess, Dinklage & Sprung ABSTRACT: Granulated initiatorexplosive composition having a weight ratio of 5:95 to 95:5 of leadazide to lead trinitroresorcinate and 0.1 to 0.5 weight percent bindercalculated on total weight of the composition.

PRlMllNG COMPGSITION This invention relates to explosive compositions.lt more particularly refers to a novel explosive composition and formuseful as an initiator.

Mixtures of lead azide with lead trinitroresorcinate have been used fora long time as initiators for detonating caps. These mixtures have,besides the considerable advantage which the extraordinary ignitionsensitivity of the lead trinitroresorcinate imparts to the mixture, alsodisadvantages as compared to using lead azide by itself. For example, itis extremely difficult to obtain homogeneous mixtures of both thesesubstances by plain mixing, and therefore in prior art it was alwaysexpected that separations would occur.

While separations towards an increased proportion of lead azide are notso critical because smaller amounts of lead trinitroresorcinate stillprovide the mixture with a sufficient ignitibility, a decrease of leadazide is feared in practice because the initiator force of the mixture,which is based alone upon the proportion of lead azide, becomesconsiderably weakened so that ignition failures may occur. In practice,this potential problem is compensated for by using a considerably higheramount above the required amount of priming mixture.

It is an object of this invention to provide an improved initiator.

Other and additional objects of this invention will become apparent froma consideration of this entire specification including the claims.

These objects can be achieved by using, in accordance with theinvention, a mixture, as a priming composition, of lead azide and leadtrinitroresorcinate granulated in the wet state with binders. It ispreferred that the ratio of lead trinitroresorcinate to lead azide isabout 5:95 to 95:5 weight percent with about 0.1 to 0.5 weight percentbinder referred to the total weight. Because of the high sensitivenessto percussion and shock of a mixture of lead azide and leadtrinitroresorcinate, the prior art did not consider production of such amixture in granulated form.

Suitable for use as binders are nitrocellulose, methyl-, ethylacetylorsimilar cellulose derivatives or alginates, guar flower and highpolymers which are water-soluble or capable of swelling with water suchas polyvinyl alcohols, polykylene glycols (ethers) or polyvinylpyrrolidenes. We would particularly like to mention nitrocellulose witha nitrogen content of l2to 14 percent and acetone-soluble acetylcellulose. The lead trinitroresorcinate particle sizes can vary fromcoarse to fine. The distribution of components in the particles isbetter in fine particle sizes. The lead azide can be added in difierentpercentages, Le, 88 percent 90 percent, 92 percent, 94 percent, and 98percent.

The granulating of the lead azide trinitroresorcinate mixtures can takeplace by precipitation of the binder from a solution (l) or by machinegranulating or by hand.

(I) GRANULATING BY PRECIPITATING THE BINDER FROM A SOLUTION In a l literkettle with stirrer (about 150 rpm, there are added 30 liters of acetoneand 300 g. of nitrocellulose are dissolved therein. When thenitrocellulose has become completely dissolved, there are added 7 kg. ofPbN and 3 kg. of lead trinitroresorcinate (in any sequence). Afteradjusting the temperature to about 20 C., about 50 liters of H 0 of thesame temperature are permitted to run into the mixture within 30minutes.

After the addition of the H 0, a post-stirring for an additional 2minutes is carried out. Thereafter, the formed cake is filtered off bysuction, washed with alcohol, and then dried at an air temperature of 40to 50 C. The dry product forms into readily flowable granules, which maybe separated by sifting into the desired granular size fractions.

The mixtures obtained in accordance with the described granulatingmethod are characterized by excellent resistance to separation. I t

Thus, 100 g. of the mixture obtained in accordance with method (I) wereloaded into a conventional loading device which was vibrated at apredetermined vibration with the aid of a vibration generator. Theanalysis showed a substantially constant ratio of the components in themixture from the beginning to the end of the loading process.

By way of comparison, there was loaded in the same apparatus the samemixture of components without binder, i.e., in nongranulated form. Themixture proportions at the beginning of the loading were relativelyhomogeneous, yet at the end of the loading procedure visiblenonhomogeneity, which could be seen by the nests of the leadtrinitroresorcinate in the yellowish-white lead azide, appeared and verydifierent proportions of components which ranged up to a mixture ratioof 1:1 leadazide/ leadtrinitroresorcinate.

The priming force of this mixture is now only at 50 percent of themixture of 70 percent lead azide and 30 percent leadtrinitroresorcinate.

A further advantage of the priming composition in accordance with theinvention is the fact that the same may be produced in large charges.Furthermore, the mixture which constitutes the initial primer is readilyflowable. The impact and friction sensitivity is strongly diminishedwithout having appreciably reduced the ignition sensitivity or priminglimit.

We claim:

1. Method for the production of explosive initiator compositionscomprising free-flowing granules of about 5 to weight percent leadazide, about 5 to 95 weight percent lead trinitroresorcinate and abinder; which method comprises forming a fluid form mixture of leadazide, lead trinitroresorcinate, a cellulose ester and a solvent forsaid cellulose ester; adding a nonsolvent liquid to said mixture in anamount and at a temperature sufficient to precipitate said lead azide,said lead trinitroresorcinate and said cellulose ester from said fluidform mixture; removing substantially all of the liquid from saidprecipitate; and recovering free-flowing granules of lead azide and leadtrinitroresorcinate in the proportions specified above which granulesare bonded by said cellulose ester.

2. Method as claimed in claim 1 wherein said cellulose ester is a memberselected from the group consisting of nitrocellulose, acetone solubleacetyl cellulose, methyl cellulose and ethyl cellulose.

3. Method as claimed in claim 1 wherein said solvent is acetone and saidprecipitant is water.

4. Method as claimed in claim 1 wherein said cellulose derivative ispresent in said admixture in a proportion of about 0.1 to 0.5 weightpercent.

2. Method as claimed in claim 1 wherein said cellulose ester is a memberselected from the group consisting of nitrocellulose, acetone solubleacetyl cellulose, methyl cellulose and ethyl cellulose.
 3. Method asclaimed in claim 1 wherein said solvent is acetone and said precipitantis water.
 4. Method as claimed in claim 1 wherein said cellulosederivative is present in said admixture in a proportion of about 0.1 to0.5 weight percent.